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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
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    <title>Document</title>
    <script>
        /* 
        if语句的使用:
            条件表达式：必须返回true或false
         */
        if(3 > 12){
            //true
            //如果该表达式满足条件，就会执行if 语句里面的代码块
            alert("满足条件")
        }
        alert("代码继续执行")
        
    </script>
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